Techniques for safely unloading externally-slung helicopter loads

Abstract

Precision hover is necessary when one must position a load precisely on the deck of a ship. Manual precision hover is possible under very light wind gust conditions and a calm sea. The techniques described here are directed to those special windy days when a mission must be accomplished. The technique is to unload a containerized cargo onto a platform kept level regardless of the rolling motions of the ship. The platform is a resilient net of the proper strength to absorb the cargo's impact upon its contact with the net. During night operations under adverse weather conditions it is desirable to remove the cargo from the hoisting mechanism manually unaided. This is accomplished by an automatic sling detachment device. Usually the container will approach the net at an angle. This is desirable, enabling one or two of the devices to detach themselves first and permitting the reduction in loading upon the helicopter to be less abrupt. As the load is lowered further all four devices will detach themselves automatically. The container may be moved elsewhere aboard the ship with the aid of a crane. If the container is not moved elsewhere, then it is placed over an inflated pad, having air relief valves, to absorb the load's impact. The pad remains until the ship's cargo is unloaded, when the pads are retrieved to be used again.

I claim: 
     
       1. A load supporting system for safely unloading a containerized load from hoisting cables onto a ship platform comprising: a rectangular - shaped net to support heavy loads while maintaining a level position along one of its two axes when supported by a platform moving angularly, said net attached to a rectangular - shaped inner frame, said inner frame supported by a rectangular outer frame by means of coiled tension springs, a stationary servo motor mounted on said ship and a tilt sensor attached to said outer frame responsive to the angular roll position of said ship in order to provide a horizontal reference, a mat having essentially a flat surface provided beneath said net for cushioning said cargo in case any part of said net should fail, said tilt sensor sensitive to any departure of said outer frame from a horizontal position along one of its two orthogonal axes, producing an output signal proportional to the magnitude of the angle of tilt from the horizontal to cause said servometer to rotate and keep said net level along one of said axes.   
     
     
       2. A load supporting system in accordance with claim 1, wherein said outer frame is prevented from twisting by said load's impact upon said net by guides attached to the center portion along said frame's longitudinal axis, said guide held in place by stationary U-shaped channels having linear bearings, friction between stationary and moving parts being reduced by said linear bearings. 
     
     
       3. A load supporting system in accordance with claim 1, wherein said net has numerous narrow bands extending from one side to the opposite side of said inner frame, the end of each band provided with means for being firmly supported by said frame, and each of said bands provided with S-shaped folds near each said end to assist in absorbing the force of impact of said load when it is lowered onto said net. 
     
     
       4. A load supporting system in accordance with claim 1, wherein said mat is air-inflated, rip-resistant and capable of withstanding and absorbing the weight of a heavy load placed upon said surface. 
     
     
       5. A load supporting system in accordance with claim 4, wherein said mat is provided with two or more air relief valves to gradually and uniformly expel its air as said load settles on said mat. 
     
     
       6. A load supporting system in accordance with claim 1, wherein said load is provided with an inflated tube surrounding its periphery, said tube being provided with at least one combination air relief and air extraction valve to remove said tube's air after said load has been placed on said ship. 
     
     
       7. A load supporting system in accordance with claim 1, wherein said load is provided with at least one automatic sling detachment device to enable said load to be freed of said hoisting cables, each said device comprising an upper part A and a lower part B: wherein upperpart A comprises and independent part having two exterior rotatable arm members and a central T-shaped support member; the lower inside end of each rotatable arm member being attached to a triangular teeth-shaped submember with the teeth pointing upwardly; the said three members being held together by a single low friction bolt; a light tension spring holding the lower end of each arm member upward, when said upper part is separated from a lower part;   wherein lower part B comprises an independent part having an upper horizontal member with a thickness greater than the thicknesses of said two rotatable arm members, having teeth pointing downwardly along its center portion to match the teeth of said arms of said upper part, said horizontal member being supported by two rods attached to the underside of said horizontal members at its opposite ends; said upper and lower parts having their upper and lower teeth in engagement when the rods of the lower part are attached to a load and said T-shaped member is under tension, such as when suspended by a hoist cable; when said teeth are engaged, said rotatable arms being aligned and said springs being extended; when said load is positioned on said platform so tension on said hoist cable is relieved, said teeth being disengaged and said rotatable arms being automatically sprung apart under the tension of the spring the two said parts, upper and lower, thus separating from each other, the engaged teeth being the only contacts keeping said parts together.   
     
     
       8. A load supporting system for safely unloading a containerized load from hoisting cables unto a loading platform comprising: 1. a sufficiently large mat having an essentially flat surface, capable of withstanding and absorbing the weight of a heavy load placed upon its surface from said hoisting cables   2. said load provided with at least one automatic sling detachment device to enable said load to be freed of said hoisting cables, each said device comprising an upper part A and a lower part B:   wherein said upper part A comprises two exterior rotatable arm members and a central T-shaped support member; the lower inside end of each rotatable arm member being attached to a triangular teeth-shaped submember with the teeth pointing upwardly; the said three members being held together by a single low friction bolt; a light tension spring holding the lower end of each arm member upward, when said upper part is separated from a lower part;   wherein each lower part comprises an independent part having an upper horizontal member with a thickness greater than the thicknesses of said two rotatable arm members, having teeth pointing downwardly along its center portion to match the teeth of said arms of said upper part, said horizontal member being supported by two rods attached to the underside of said horizontal member at its opposite ends; said upper and lower parts having their upper and lower teeth in engagement when the rods of the lower part are attached to a load and said T-shaped member is under tension, such as when suspended by a hoist cable; when said teeth are engaged, said rotatable arms being aligned with said springs being extended; when said load is positioned on said platform so tension on said hoist cable is relieved, said teeth being disengaged and said rotatable arms being automatically sprung apart under tension of the spring; and the two said parts, upper and lower, thus separating from each other, the engaged teeth being the only contacts keeping said parts together.   
     
     
       9. A load supporting system in accordance with claim 8, wherein said containerized load is lowered in the midst of other containerized loads at said loading platform and is provided with an inflated tube surrounding said load's periphery to protect said load and an adjacent load, should one load collide against the other load; said inflated tube being fitted with an air relief valve. 
     
     
       10. A load supporting system in accordance with claim 8, wherein said mat is air-inflated, rip-resistant, has compartmentalized portions and is provided with two or more air relief valves to gradually and uniformly expel its air, as said load settles on said mat, and wherein air is permitted to pass from one compartmentalized portion to another. 
     
     
       11. A load supporting system in accordance with claim 1, wherein said load is provided with at least one automatic sling detachment device to enable said load to be freed of said hoisting cables, each said device comprising an upper part A and a lower part B: wherein said upper part A comprises two exterior rotatable arm members and a central T-shaped support member; the lower inside end of each rotatable arm member being attached to a triangular teeth-shaped submember with the teeth pointing upwardly; the said three members being held together by a single low friction bolt; each of said rotatable arm members having an extention beyond said bolt and a suitable weight being pivoted at the upper end of each said extention; wherein said lower part B comprises an independent part having an upper horizontal member with a thickness greater than the thickness of said two rotatable arm members, having teeth pointing downwardly along its center portion to match the teeth of said arms of said upper part, said horizontal member being supported by two rods attached to the underside of said horizontal members at its opposite ends; said upper and lower parts having their upper and lower teeth in engagement when the rods of the lower part are attached to a load and said T-shaped member is under tension, such as when suspended by a hoist cable; when said teeth are engaged, said rotatable arms being aligned and each said suitable weight being alinged in the same traverse plane, when said load is positioned on said platform so tension on said hoist cable is relieved, said teeth being disengaged and said rotatable arms being automatically rotated by the mass of the weight, the two said parts, upper and lower, thus separating from each other, the engaged teeth being the only contacts keeping said parts together.